1. Field of Invention
This invention relates to absorbable coated suture and particularly to an absorbable composition useful as a lubricating finish for surgical sutures. More particularly, this invention relates to a means for improving the tie-down properties of synthetic absorbable multifilament sutures by coating the sutures with an absorbable composition.
2. Description of Prior Art
Suture materials are generally classified as either absorbable or non-absorbable, with each type of suture material being preferred for certain applications. Absorbable suture materials are preferred for applications in which the sewn tissues after healing will hold together without suture reinforcement and in which a non-absorbed suture may provide the possibility of an adverse bodily reaction over an extended period of time. Suture materials are considered to be absorbable if they disappear from the sewn tissue within a year after surgery, but most absorbable suture materials preferably disappear within shorter periods.
The most commonly used absorbable suture materials are catgut and extruded collagenous materials. More recently sutures derived from synthetic polymers have been developed which are absorbable, strong, uniform and dimensionally stable, storable in the dry state and sterilizable. Typical of such polymers are lactide homopolymers and copolymers such as those disclosed in U.S. Pat. No. 3,636,956, issued to Allan K. Schneider on Jan. 25, 1972, and glycolide homopolymers such as those disclosed in U.S. Pat. No. 3,297,033, issued to Edward Emil Schmitt et al on Jan. 10, 1967, both patents being incorporated herein by reference.
Monofilament synthetic absorbable suture materials are generally stiffer than their catgut or collagen counterparts, and synthetic absorbable sutures are therefore usually employed in a braided, multifilament construction. Such multifilament sutures exhibit a certain degree of undesirable roughness or "grabbiness" in what has been termed their "tie-down" performance, i.e., the ease or difficulty of sliding a knot down the suture into place.
Multifilament non-absorbable sutures, such as braided sutures of polyethylene terephthalate for example, can be improved with respect to tie-down performance by depositing solid particles of polytetrafluoroethylene and a binder resin on the external surface of the suture as disclosed in U.S. Pat. No. 3,527,650. This procedure, however, is undesirable as applied to absorbable sutures because polytetrafluoroethylene is nonabsorbable and sutures coated therewith would leave a residue in the sewn tissue.
Multifilament non-absorbable sutures can also be improved with respect to tie-down performance by coating them with a linear polyester having a molecular weight between about 1,000 and about 15,000 and at least two carbon atoms between the ester linkages in the polymer chain as disclosed in copending and coassigned U.S. patent application Ser. No. 303,588, now abandoned. Said application discloses that the aforementioned polyesters may also be used to coat absorbable synthetic sutures but does not consider that such coated sutures would not be totally absorbable.
The aforementioned U.S. Pat. No. 3,297,033 discloses that the synthetic absorbable sutures described therein may be coated with coating materials used on conventional sutures, such as a silicone or beeswax to modify the handling or absorption rate of the sutures. These coating materials are non-absorbable and will accordingly leave an undesirable residue in the tissue after the suture itself is absorbed.
It is accordingly an object of the present invention to provide an absorbable coating for multifilament sutures of braided, twisted or covered construction. It is a further object of this invention to provide an absorbable coating to improve the tie-down properties of such multifilament sutures. It is a yet further object of this invention to provide a wholly absorbable coated synthetic multifilament suture having good tie-down properties.